Greatly aided by its successful Soviet Alsos and the atomic spies, the Soviet Union conducted its first weapon test of an implosion-type nuclear device, RDS-1, codenamed First Lightning, on 29 August 1949, at Semipalatinsk, Kazakh SSR. With the success of this test, the Soviet Union became the second nation after the United States to detonate a nuclear device.

In early 1930s, the Soviets were instrumental to the advancement of nuclear physics. The Soviet interest in nuclear physics had begun in the early 1930s, an era in which a variety of important nuclear discoveries and achievements were made (such as the identification of the neutron as fundamental particles, the operation of the first cyclotron to energies of over 1 MeV, and the first "splitting" of the atomic nucleus (atom) by John Cockcroft and Ernest Walton). Even before the Russian revolution and the February Revolution, the mineralogist Vladimir Vernadsky had made a number of public calls for a survey of Russia's uranium deposits.[citation needed] The main motivation for nuclear research at the time was radium, which had scientific as well as medical uses, and could be retrieved from borehole water from the Ukhta oilfields.

After the discovery of nuclear fission in the late 1930s, Soviet scientists, like scientists all over the world, realized that nuclear reactions could, in theory, be used to release large amounts of binding energy. As in the West, the news of fission created great excitement amongst Soviet scientists and many physicists switched their lines of research to those involving nuclear physics, as it was considered a promising field of research. Soviet nuclear research was not far behind Western scientists: Yakov Frenkel did the first theoretical work on fission in the Soviet Union in 1940, and Georgy Flyorov and Lev Rusinov concluded that 3-1 neutrons were emitted per fission only days after similar conclusions had been reached by the team of Frédéric Joliot-Curie.[citation needed]

The soviet Atomic Bomb Project has its roots all the way back in the 1910s, when Russia began researching radioactive materials. The research being done was not officially institutionalized until 1922 when the Radium Institute in Petrograd opened. Through the thirties there were various other institutions opened across the nation. It is important to acknowledge that the research and institutions were all a part of civil society. This meant that the military did not directly control the progress being made.

In 1940, a commission was set up to address the Uranium Problem allowing intelligentsia to study nuclear fission and Uranium. Although significant ground had been broke the majority of research would be abandoned during World War II. Russia would spend the next four years in conflict with Europe and the West.

Soviet physicist Georgy Flyorov noticed that in spite of the progress German, British and American physicists had made in research into uranium fission, scientific journals had ceased publishing papers on the topic. Flyorov deduced that this meant such research had been classified, and wrote to Stalin in April 1942. He cited the lack of response he had himself encountered trying to generate interest in similar research, and warned Stalin of the consequences of the development of atomic weapons: "...the results will be so overriding [that] it won't be necessary to determine who is to blame for the fact that this work has been neglected in our country." By September 1942, Stalin, who had already been presented with evidence of the Western nuclear programs in the MAUD Report of 1940, decided to launch a Soviet program to develop an atomic bomb headed by Igor Kurchatov. Creation in 1943 of Laboratory No. 2 under the Academy of Sciences of the USSR was the first stage of the Soviet atomic bomb project.

In the wake of the atomic bombing of the Japanese cities of Hiroshima and Nagasaki in 1945, Stalin made the decision to accelerate research and development, expanding the development of military nuclear reactors and research facilities all over the country. When the United States tested the Atom Bomb in 1945 Stalin decided to push the intellectuals even harder. They appointed a special committee that was fully funded. This committee was headed by Beria who was now in charge of a large group of specialists in science and industry. Again it is important to make note that Stalin did not include military men. Instead he put those from the party, civilians, and secret police in charge.

Early ideas of the fusion bomb came from espionage and internal Soviet studies. Though the espionage did help Soviet studies, the early American H-bomb concepts had substantial flaws, so it may have confused, rather than assisted, the Soviet effort for a nuclear bomb.[1] The designers of early thermonuclear bombs envisioned using an atomic bomb as a trigger to provide the needed heat and compression to initiate the thermonuclear reaction of a layer liquid deuterium between the fissile material and the surrounding chemical high explosive.[2] The group would realize that a lack of sufficient heat and compression of the deuterium would result in an insignificant fusion of the deuterium fuel.[2]

Andrei Sakharov’s study group at FIAN in 1948 came up with a second concept which was adding a shell of natural, unenriched uranium around the deuterium would increase the deuterium concentration at the uranium-deuterium boundary and the overall yield of the device, because the natural uranium would capture neutrons and itself fission as part of the thermonuclear reaction. This idea of a layered fission-fusion-fission bomb led Sakharov to call it the sloika, or layered cake.[2] It was also known as the RDS-6S, or Second Idea Bomb.[3] This second bomb idea was not a fully evolved thermonuclear bomb in the contemporary sense, but a crucial step between pure fission bombs and the thermonuclear “supers.”[4] Due to the three-year lag in making the key breakthrough of radiation compression from the United States the Soviet Union’s development efforts followed a different course of action. In the United States they decided to skip the single-stage fusion bomb and make a two-stage fusion bomb as their main effort.[2][5] Unlike the Soviet Union, the analog RDS-7 advanced fission bomb was not further developed, and instead, the single-stage 400-kiloton RDS-6S was the Soviet’s bomb of choice.[2] The RDS-6S Layer Cake design was detonated on 12 August 1953, producing a yield of 400 kilotons, about ten times more powerful than any previous Soviet test. Around this time the United States detonated its first super using radiation compression on 1 November 1952, code-named Mike. Though the Mike was about twenty times greater than the RDS-6S it was not a design that was practical to use, unlike the RDS-6S.[2]

Following the successful launching of the RDS-6S Sakharov proposed an upgraded version called RDS-6SD.[2] This bomb was proved to be faulty, and it was neither built nor tested. The Soviet team had been working on the RDS-6T concept, but it also proved to be a dead end. In 1954, Sakharov worked on a third concept, a two-stage thermonuclear bomb.[2] The third idea used the radiation wave of a fission bomb, not simply heat and compression, to ignite the fusion reaction, and paralleled the discovery made by Ulam and Teller. Unlike the RDS-6S boosted bomb, which placed the fusion fuel inside the primary A-bomb trigger, the thermonuclear super placed the fusion fuel in a secondary structure a small distance from the A-bomb trigger, where it was compressed and ignited by the A-bomb’s x-ray radiation.[2] The KB-11 Scientific-Technical Council approved plans to proceed with the design on 24 December 1954. Technical specifications for the new bomb were completed on 3 February 1955, and it was designated the RDS-37.[2]

The RDS-37 was successfully tested on 22 November 1955 with a yield of 1.6 megaton. The yield was almost a hundred times greater than the first Soviet atomic bomb six years before, showing that the Soviet Union could compete with the United States.[2][6]

The Soviet atomic project benefited from highly successful espionage efforts on the part of the GRU and the foreign intelligence department of the NKVD. Evidence from intelligence sources in the United Kingdom had a role to play in the decision of the Soviet State Defense Committee, in September 1942, to approve resolution 2352, which signaled the beginning of the Soviet atom bomb project.

Through sources in the Manhattan Project, notably Klaus Fuchs, the Soviet intelligence obtained important information on the progress of the United States atomic bomb effort. Intelligence reports were shown to the head of the Soviet atomic project and had a significant impact on the direction of Soviet research.

For example, Soviet work on methods of uranium isotope separation was altered when it was reported, to Kurchatov's surprise, that the Americans had opted for the Gaseous diffusion method. While research on other separation methods continued throughout the war years, the emphasis was placed on replicating U.S. success with gaseous diffusion. Another important breakthrough, attributed to intelligence, was the possibility of using plutonium, instead of uranium, in a fission weapon. Extraction of plutonium in the so-called "uranium pile" allowed the bypass of the difficult process of uranium separation altogether — something that Kurchatov had learned from intelligence from the Manhattan project.[citation needed]

In 1945, the Soviet intelligence obtained rough blueprints of the first U.S. atomic device.[7][8] Alexei Kojevnikov has estimated, based on newly released Soviet documents, that the primary way in which the espionage may have sped up the Soviet project was that it allowed Khariton to avoid dangerous tests to determine the size of the critical mass: "tickling the dragon's tail," as it was called in the U.S., consumed a good deal of time and claimed at least two lives; see Harry Daghlian and Louis Slotin.

The published Smyth Report of 1945 on the Manhattan Project was translated into Russian, and the translators noted that a sentence on the effect of "poisoning" of Plutonium-239 in the first (lithograph) edition had been deleted from the next (Princeton) edition by Groves. This change was noted by the Russian translators, and alerted the Soviet Union to the problem (which had meant that reactor-bred plutonium could not be used in a simple gun-type bomb like the proposed Thin Man).

One of the key pieces of information, which Soviet intelligence obtained from Fuchs, was a cross-section for D-T fusion. This data was available to top Soviet officials roughly three years before it was openly published in the Physical Review in 1949. However, this data was not forwarded to Vitaly Ginzburg or Andrei Sakharov until very late, practically months before publication.[citation needed] Initially both Ginzburg and Sakharov estimated such a cross-section to be similar to the D-D reaction. Once the actual cross-section become known to Ginzburg and Sakharov, the Sloika design become a priority, which resulted in successful test in 1953.

In the 1990s, with the declassification of Soviet intelligence materials, which showed the extent and the type of the information obtained by the Soviets from US sources, a heated debate ensued in Russia and abroad as to the relative importance of espionage, as opposed to the Soviet scientists' own efforts, in the making of the Soviet bomb. The vast majority of scholars[whom?] agree that whereas the Soviet atomic project was first and foremost a product of local expertise and scientific talent, it is clear that espionage efforts contributed to the project in various ways and most certainly shortened the time needed to develop the atomic bomb.[citation needed]

Comparing the timelines of H-bomb development, some researchers came to a conclusion that Soviets had a gap in access to classified information regarding the H-bomb at least between late 1950 and some time in 1953. Earlier, e.g., in 1948, Fuchs gave to the Soviets a detailed update of the classical super progress, including an idea to use lithium, but did not explain it was specifically lithium-6. Teller accepted the fact that "classical super" scheme was infeasible by 1951, following results obtained by various researchers (including Stanislaw Ulam) and calculations performed by John von Neumann in late 1950.

Yet the research for the Soviet analogue of "classical super" continued until December 1953, when the researchers were reallocated to a new project working on what later became a true H-bomb design, based on radiation implosion. It remains an open topic for research, whether the Soviet intelligence was able to obtain any specific data on Teller-Ulam design in 1953 or early 1954. Yet, Soviet officials directed the scientists to work on a new scheme, and the entire process took less than two years, commencing around January 1954 and producing a successful test in November 1955. It also took just several months before the idea of radiation implosion was conceived, and there is no documented evidence claiming priority. It is also possible that Soviets were able to obtain a document lost by John Wheeler on a train in 1953, which reportedly contained key information about thermonuclear weapon design.

The single largest problem during the early Soviet project was the procurement of uranium ore, as the USSR had no known domestic sources at the beginning of the project. The Soviet F-1 reactor, which began operation in December 1946, was fueled using uranium confiscated from the remains of the German atomic bomb project. This uranium had been mined in the Belgian Congo, and the ore in Belgium fell into the hands of the Germans after their invasion and occupation of Belgium in 1940 (although Edgar Sengier sold the rich Shinkolobwe ore from the Congo, some of which was held in America, to America). Further sources of uranium in the early years of the program were mines in East Germany (SAG Wismut), Czechoslovakia, Bulgaria, Romania (near Stei) and Poland. Boris Pregel sold 0.23 tonnes of uranium oxide to the Soviet Union during the war, with the authorisation of the U.S. Government.[9]

Eventually large domestic sources were discovered in the Soviet Union (including those now in Kazakhstan).

The uranium for the Soviet nuclear weapons program came from mine production in the following countries,[10]

RDS-1, the first Soviet atomic test was internally code-named First Lightning (Первая молния, or Pervaya Molniya) August 29, 1949, and was code-named by the Americans as Joe 1. The design was very similar to the first US "Fat Man" plutonium bomb, using a TNT/hexogen implosion lens design.

The mushroom cloud from the first air-dropped bomb test in 1951. This picture is confused with RDS-27 and RDS-37 tests.

RDS-3 was the third Soviet atomic bomb. On October 18, 1951, the 41.2 kiloton device was detonated - a boosted weapon using a composite construction of levitated plutonium core and a uranium-235 shell. Code named Joe 3 in the USA, this was the first Soviet air-dropped bomb test. Released at an altitude of 10 km, it detonated 400 meters above the ground.

RDS-4 represented a branch of research on small tactical weapons. It was a boosted fission device using plutonium in a "levitated" core design. The first test was an air drop on August 23, 1953, yielding 28 kilotons. In 1954, the bomb was also used during Snowball exercise in Totskoye, dropped by Tu-4 bomber on the simulated battlefield, in the presence of 40,000 infantry, tanks, and jet fighters. The RDS-4 comprised the warhead of the R-5M, the first medium-range ballistic missile in the world, which was tested with a live warhead for the first and only time on February 5, 1956

RDS-6, the first Soviet test of a hydrogen bomb, took place on August 12, 1953, and was nicknamed Joe 4 by the Americans. It used a layer-cake design of fission and fusion fuels (uranium 235 and lithium-6 deuteride) and produced a yield of 400 kilotons. This yield was about ten times more powerful than any previous Soviet test.[2] When developing higher level bombs the Soviets proceeded with the RDS-6 as their main effort instead of the analog RDS-7 advanced fission bomb. This led to the third idea bomb which is the RDS-37.[2]

A much lower-power version of the RDS-4 with a 3-10 kiloton yield, the RDS-9 was developed for the T-5 nuclear torpedo. A 3.5 kiloton underwater test was performed with the torpedo on September 21, 1955.

The first Soviet test of a "true" hydrogen bomb in the megaton range was conducted on November 22, 1955. It was dubbed RDS-37 by the Soviets. It was of the multi-staged, radiation implosion thermonuclear design called Sakharov's "Third Idea" in the USSR and the Teller-Ulam design in the USA.[12]

The Tsar Bomba (Царь-бомба) was the largest, most powerful nuclear weapon ever detonated. It was a three-stage hydrogen bomb with a yield of about 50 megatons.[13] This is equivalent to ten times the amount of all the explosives used in World War II combined.[14] It was detonated on October 30, 1961, in the Novaya Zemlyaarchipelago, and was capable of approximately 100 megatons, but was purposely reduced shortly before the launch. Although weaponized, it was not entered into service; it was simply a demonstrative testing on the capabilities of the Soviet Union's military technology at that time. The explosion was hot enough to induce third degree burns at 100 km distance.[15]

During the Cold War the Soviet Union created at least nine closed cities, known as Atomgrads[citation needed], in which nuclear weapons-related research and development took place. After the dissolution of the Soviet Union, all of the cities changed their names (most of the original code-names were simply the oblast and a number). All are still legally "closed", though some have parts of them accessible to foreign visitors with special permits (Sarov, Snezhinsk, and Zheleznogorsk).

The Soviets started experimenting with nuclear technology in 1943, and first tested a nuclear weapon in August 1949. Many of the fission based devices left behind radioactive isotopes which have contaminated air, water and soil in the areas immediately surrounding, downwind and downstream of the blast site. According to the records that the Russian government released in 1991, the Soviet Union tested 969 nuclear devices between 1949 and 1990.[16]:1 Soviet scientists conducted the tests with little regard for environmental and public health consequences. The detrimental effects that the toxic waste generated by weapons testing and processing of radioactive materials are still felt to this day. Even decades later, the risk of developing various types of cancer, especially that of the thyroid and the lungs, continues to be elevated far above national averages for people in affected areas.[17]:1385Iodine-131, a radioactive isotope that is a major byproduct of fission-based weapons, is retained in the thyroid gland, and so poisoning of this kind is commonplace in impacted populations.[17]:1386

The Soviets set off 214 nuclear bombs in the open air between 1949 and 1962, when the United Nations banned atmospheric tests worldwide.[16]:6 The billions of radioactive particles released into the air exposed countless people to extremely mutagenic and carcinogenic materials, resulting in a myriad of deleterious genetic maladies and deformities. The majority of these tests took place at the Semipalatinsk Test Site, or STS, located in northeast Kazakhstan.[16]:61 The testing at STS alone exposed hundreds of thousands of Kazakh citizens to the harmful effects, and the site continues to be one of the most highly irradiated places on the planet.[18]:A167 When the earliest tests were being conducted, even the scientists had only a poor understanding of the medium- and long-term effects of radiation exposure. In fact, the STS was chosen as the primary site for open-air testing precisely because the Soviets were curious about the potential for lasting harm that their weapons held.[17]:1389

Contamination of air and soil due to atmospheric testing is only part of a wider issue. Water contamination due to improper disposal of spent uranium and decay of sunken nuclear-powered submarines is a major problem in the Kola Peninsula in northwest Russia. Although the Russian government states that the radioactive power cores are stable, various scientists have come forth with serious concerns about the 32,000 spent nuclear fuel elements that remain in the sunken vessels.[18]:A166 There have been no major incidents other than the explosion and sinking of a nuclear-powered submarine in August 2000, but many international scientists are still uneasy at the prospect of the hulls eroding, releasing uranium into the sea and causing considerable contamination.[18]:A166 Although the submarines pose an environmental risk, they have yet to cause serious harm to public health. However, water contamination in the area of the Mayak test site, especially at Lake Karachay, is extreme, and has gotten to the point where radioactive byproducts have found their way into drinking water supplies. It has been an area of concern since the early 1950s, when the Soviets began disposing of tens of millions of cubic meters of radioactive waste by pumping it into the small lake.[18]:A165 Half a century later, in the 1990s, there are still hundreds of millions of curies of waste in the Lake, and at points contamination has been so severe that a mere half-hour of exposure to certain regions would deliver a dose of radiation sufficient to kill 50% of humans.[18]:A165 Although the area immediately surrounding the lake is devoid of population, the lake has the potential to dry up in times of drought. Most significantly, in 1967, it dried up and winds carried radioactive dust over thousands of square kilometers, exposing at least 500,000 citizens to a range of health risks.[18]:A165 To control dust, Soviet scientists piled concrete on top of the lake. Although this was effective in helping mediate the amount of dust, the weight of the concrete pushed radioactive materials into closer contact with standing underground groundwater.[18]:A166 It is difficult to gauge the overall health and environmental effects of the water contamination at Lake Karachay because figures on civilian exposure are unavailable, making it hard to show causation between elevated cancer rates and radioactive pollution specifically from the lake.

Contemporary efforts to manage radioactive contamination in the Soviet Union are few and far between. Public awareness of the past and present dangers, as well as the Russian government's investment in current cleanup efforts, are likely dampened by the lack of media attention STS and other sites have gotten in comparison to isolated nuclear incidents such as Hiroshima, Nagasaki, Chernobyl and Three-Mile Island.[19] The domestic government's investment in cleanup measures seems to be driven by economic concerns rather than care for public health. The most significant political legislation in this area is a bill agreeing to turn the already contaminated former weapons complex Mayak into an international radioactive waste dump, accepting cash from other countries in exchange for taking their radioactive byproducts of nuclear industry.[18]:A167 Although the bill stipulates that the revenue go towards decontaminating other test sites such as Semipalatinsk and the Kona Peninsula, experts doubt whether this will actually happen given the current political and economic climate in Russia.[18]:A168

^The American counterpart to this idea was Edward Teller's Alarm Clock design of August 1946. In August 1990 the Soviet science journal Priroda published a special issue devoted to Andrei Sakharov, which contained more detailed notes on the early fusion bomb than Sakharov's own memoirs, especially the articles by V.E. Ritus and Yu A. Romanov

^The Super Oralloy bomb was developed in Los Alamos and tested on 15 November 1952

^Details of Soviet weapons designs after 1956-57 are generally lacking. A certain amount can be inferred from data about missile warheads, and in recent histories, the two nuclear-warhead development bureaus have begun to cautiously reveal which weapons they designed.

^The yield of the test has been estimated between 50 and 57.23 megatons by different sources over time. Today all Russian sources use 50 megatons as the official figure. See the section "Was it 50 Megatons or 57?" at "The Tsar Bomba ("King of Bombs")". Retrieved 11 May 2006.